Structural insights into the organization of the human Erlin complex

Area of Science:

• Cell Biology
• Structural Biology
• Biochemistry

Background:

• Endoplasmic reticulum (ER) lipid raft proteins (Erlins) are SPFH family members.
• Erlins form oligomeric platforms involved in protein degradation.
• The precise molecular mechanisms of Erlin function remain elusive.

Purpose of the Study:

• To elucidate the structural basis of Erlin complex assembly and function.
• To investigate the interaction between Erlins and the E3 ligase RNF170.

Main Methods:

• Reconstitution of Erlin1-Erlin2 and Erlin1-Erlin2-RNF170 complexes in HEK293F cells.
• Isolation of Erlin2 oligomers.
• Cryo-electron microscopy (cryo-EM) for structural determination.

Main Results:

• Determined cryo-EM structures of Erlin1-Erlin2 complex (3.29 Å), Erlin1-Erlin2-RNF170 complex (3.05 Å), and Erlin2 oligomer (2.12 Å).
• Both Erlin1-Erlin2 complex and Erlin2 oligomer feature cage-like architectures.
• RNF170 was not visible in the final reconstruction, indicating high flexibility.

Conclusions:

• Structural insights into the assembly of Erlin complexes.
• Identified water molecules in Erlin2 oligomers, crucial for oligomerization.
• Provides a structural framework for understanding Erlin-mediated protein degradation.